The chief objective of this grant renewal is to evaluate the cancer program of the Mayo Clinic through the use of a large cancer data resource recently developed. Closely related are the objectives of cooperating with NCI, with the Centralized Cancer Patient Data System (CCPDS) and with the Statistical Analysis and Quality Control Center (SAQC) in creating for the United States a group of cancer data systems of great quality, completeness and uniformity. The initial grant (now in its third year) has been highly successful in producing the Mayo Clinic Patient Data System (MCPDS). This is an active data set of some 40,000 cancer patients, 28,000 alive, followed with over 96% completeness. MCPDS is by far the largest single contributor to SAQC among the cooperating comprehensive cancer centers. Out of a total of 20,000 cases Mayo has submitted 6,000. Now after two years of extensive development MCPDS is ready to go into production of data, reports, analyses and general evaluation of the Mayo Clinic cancer program. The second three year period covered by this request will be devoted to extending the scope of data for selected cancers, increasing follow-up items, doing special studies and continuing a high level of cooperation with CCPDS and SAQC.